Various approaches are known in order to be able to determine as exactly as possible this own position of a recording camera. For example, patent specification EP 0 909 100 B1 discloses the determination of the own position of a recording television camera directly from the image of that television camera. In the process, points of a special pattern within a virtual studio are used, as well as virtual objects.
However, patterns in the image of the recording camera often may not suffice to reliably determine the own position of that camera in every situation. This may be the case particularly in zooming situations, in which only few or no measuring points at all are visible outside of the zoomed-in object. Thus, the patent application GB 2 329 292 A, for example, proposes to provide the recording camera with an additional measuring camera that recognizes LEDs in the scene.
The position of these LEDs was measured in advance, so that the measuring camera's own position can thus be determined. The associated television camera's own position can then be indirectly determined from this, because the position of the measuring camera with respect to the television camera is fixed and known.
The patent application GB 2 325 807 A, for example, also discloses a system in which a recording camera is provided with an auxiliary camera orientated in the direction of the ceiling of the studio in order to recognize patterns on the ceiling. From this, the auxiliary camera's own position can again be determined, and thus indirectly also the recording camera's own position.
Furthermore, it is known from the patent application EP 1 594 322 A2 to determine a camera's own position without any additional markers or patterns in the studio, with, however, a plurality of reference images of the scene being recorded in different camera positions and stored prior to the recording. During the actual recording by the camera, these reference images can then be used and compared with the currently recorded images in order thus to determine the respective own position of the camera.
Moreover, sensors on the camera can be used in order to detect movements of the camera and thus draw conclusions as to the changed own position of the camera or to support a different determination of the own position. In the case of cameras with a fixed focal length, it is also known to determine the camera's own position based on known points, markings, patterns etc, wherein 2D and 3D patterns can be used.
In particular, the results of a calculation of position with an additional measuring camera and markers in space, however, depend to a great extent on the quality of the measuring camera. Usually, large aperture angles have to be used in the process, so that the camera sees much of the scene to be recorded and is able to detect as many marking points as possible despite various obstacles. However, a large aperture angle means a lower spatial resolution, so that the calculations may thus be very noisy and insufficiently exact. Especially in the field of television, however, imaging cameras with a very long focal length are often used in order to be able to zoom in very closely on objects. The longer the focal length, the more likely is it that noise or displacement of the virtual objects due to an insufficiently exact calculation of the position of the virtual images becomes visible, which is very disadvantageous, so that methods of this type can be used only to a very limited extent in the field of television.